JPH06310499A - Processing method for thin film - Google Patents

Abstract

PURPOSE:To make it possible to remove transparent thin films at high speed with visible laser. CONSTITUTION:Parallel laser light 4, projected from a laser oscillator 7, is bent by a bending mirror 8 and turned into focused laser light 6 by a focusing lens 5. The focused laser light 6 is then applied to specified areas 3 on the transparent thin film 2 formed on the surface of a glass substrate 1, and the areas 3 are thus removed. At that time the thickness, t of the transparent thin film is controlled so that t is within the range of (lambda/2n)+ or -15%, where lambda is the wavelength of the focused laser light 6 and (n) is the refractive index of the transparent thin film 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a thin film with laser light.

[0002]

2. Description of the Related Art In recent years, processing technology using laser light has made rapid progress, and cutting of metal plates by carbon dioxide gas laser, punching and precision welding of thin metal plates by YAG laser have been widely spread in the metal processing industry. ing. Also, when processing thin films such as liquid crystal display panels, thin film sensors, and semiconductor photomasks, harmonics of excimer lasers, argon ion lasers, and YAG lasers are used to reduce damage to the processed parts and to miniaturize the processed parts. From visible light to ultraviolet light, that is, lasers with a relatively short wavelength, are beginning to be used, and this tendency is expected to become stronger.

Utilization of laser processing in a liquid crystal display panel production process is utilized for processing a transparent electrode pattern on a glass substrate. Specifically, the YAG laser cuts and corrects short-circuit defects between adjacent patterns that occur when patterning a transparent electrode by the photolithography method. This technology has two methods of using the fundamental wave and the second harmonic of the YAG laser, but the use of the second harmonic with a short wavelength is used to reduce the size of the processed part and damage to the underlying glass substrate. Are being considered.

[0004]

However, in order to obtain the second harmonic of the YAG laser, a nonlinear optical crystal is used as described on page 72 of "Laser application engineering" edited by the Ministry of International Trade and Industry. Although it will be wavelength conversion, its conversion efficiency is low and it is difficult to obtain high output,
In the first place, the transparent electrode thin film, which is highly transparent to visible light, is processed with the second harmonic of a YAG laser that oscillates at the wavelength of visible light, so the energy utilization efficiency is poor and it can only be applied to local removal processing. there were.

The present invention solves the problems described above,
The purpose is to significantly improve the energy utilization efficiency when processing a transparent thin film with a visible light laser to realize high-speed processing, and to enable thin film patterning, a technology that was previously only available for local processing. To do.

[0006]

The above-mentioned object can be achieved by absorbing the energy of the laser beam to be irradiated to the processed portion as much as possible, but the thin film processing method of the present invention is a processed object. 42.5 of the wavelength of the visible light laser irradiated by the optical path length expressed by the product of the thickness of the transparent thin film and the refractive index
% To 57.5%, so that multiple reflection is performed within the workpiece. The visible light laser is also a second harmonic of a YAG laser.

[0007]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view for explaining the processing principle of an embodiment of the present invention. On the surface of the glass substrate 1, a transparent thin film 2 which is a workpiece is formed. The transparent thin film 2 has a thickness of 0.13 micrometer and is made of ITO which is generally used for liquid crystal display panels. The parallel laser light 4 emitted from the laser oscillator 7 is bent by a bending mirror 8 and is focused by a condenser lens 5 to become a condensed laser light 6 which irradiates the work piece 3. At this time, the YAG laser second harmonic having an oscillation wavelength of 0.532 micrometers and an average output of 4 W was used for the laser oscillator 7. In the actual processing, since the transparent thin film 2 was not processed by continuous oscillation of 4 W, pulse oscillation was performed by the Q switch and processing was performed with energy of 35 microjoule per pulse at a repetition frequency of 30 KHz. The processed portion 3 of the transparent thin film 2 could be removed. At this time, the surface of the glass substrate 1 was not damaged at all. This is a value obtained by multiplying the thickness of the transparent thin film 2 by 0.13 micrometer and the refractive index 2 to be 0.26 micrometer, which corresponds to the optical path length of the condensed laser beam 6 passing through the transparent thin film 2. However, since this value corresponds to about half of the wavelength 0.532 micrometer of the condensed laser beam 6, the condensed laser beam 6 is repeatedly reflected in the transparent thin film 2 to absorb energy. The efficiency was remarkably increased, and complete removal was possible with less energy. Further, since the condensed laser light 6 is sufficiently absorbed in the transparent thin film 2, leakage of the laser light to the underlying glass substrate 1 is reduced, so that processing damage does not occur. FIG. 2 is a graph showing the spectral transmittance characteristics of the transparent thin film 2 used in this example. From this graph, it can be seen that the transmittance of the transparent thin film 2 at the wavelength of the condensed laser beam 6 used for processing, 0.532 micrometer, is about 93%. That is, the amount of the condensed laser beam 6 absorbed when passing through the transparent thin film 2 is only 7%.
In the present embodiment, the passing optical path length of the condensed laser light 6 is set in consideration of the thickness and the refractive index of the transparent thin film 2.
Since it is set to 50% of the wavelength, the condensed laser light 6 is multiply reflected in the transparent thin film 2. When the amount of passing light at this time was experimentally measured, 30% of the incident energy was absorbed. FIG. 3 is a perspective view of a thin film processing apparatus according to an embodiment of the present invention. The configuration of the device will be described below. The parallel laser light 4 emitted from the laser oscillator 7 is bent downward by the bending mirror 8, condensed by the condenser lens 5, and irradiated onto the surface of the transparent thin film 2 on the glass substrate 1 which is the workpiece. It is structured. The glass substrate 1 is fixed on a moving table 9 which is uniaxially moved by a pulse motor 10 and a ball screw 11. In the thin film processing apparatus with this configuration, the oscillation laser wavelength is 0.532 micrometers and the Q switch repetition frequency is 30 KH.
z, a pulse energy of 35 microjoules per shot, and a transparent thin film 2 of ITO having a thickness of 0.13 micrometer, a cutting width of 10 micrometers and a cutting speed of 2
00 millimeters per second was obtained.

[0008]

As described above, according to the present invention, the fundamental phenomenon that energy absorption is low, which is a problem when processing a transparent thin film with a laser for processing in the visible region, is applied to a workpiece. It became possible to pass through a certain transparent thin film many times, and it became possible to remarkably enhance the energy absorption efficiency. In addition, this enabled the processing of transparent thin films with less laser light power, and the processing speed was also increased. Furthermore, since the energy of the laser beam is effectively absorbed by the transparent thin film, damage to the substrate that is the base of the transparent thin film is eliminated, and high-quality processing becomes possible.

[Brief description of drawings]

FIG. 1 is a sectional view showing a processing principle of an embodiment of the present invention.

FIG. 2 is a diagram showing a spectral transmittance characteristic of ITO in an example of the present invention.

FIG. 3 is a perspective view showing a thin film processing apparatus of one embodiment of the present invention.

[Explanation of symbols]

 1 Glass Substrate 2 Transparent Thin Film 3 Processed Part 4 Parallel Laser Light 5 Condensing Lens 6 Condensing Laser Light 7 Laser Oscillator 8 Bending Mirror 9 Moving Table 10 Pulse Motor 11 Ball Screw

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01S 3/00 B 8934-4M

Claims (2)

[Claims] 1. A processing method for removing a transparent thin film having a refractive index n formed on a substrate by laser light oscillating at a wavelength in the visible region, wherein the thickness t of the transparent thin film is (λ / 2n) ± 15% of the range, the thin film processing method. 2. The method of processing a thin film according to claim 1, wherein the laser light is a second harmonic of a YAG laser.